Dr. McLeod, MD, MSCE is a junior investigator in pediatric hospital medicine with advanced training in clinical epidemiology and quantitative analyses. Her research is focused on the comparative effectiveness of interventions for preventing surgical site infections (SSI) following spinal fusion operations in children, with an emphasis on the association between elements of the organizational contexts of care and patient-centered outcomes. In the K99 portion of this proposal, Dr. McLeod describes a multi-disciplinary career development program that will build on her existing skills and will provide advanced training in qualitative and mixed method research, quasi-experimental study designs, and implementation science, all of which will be instrumental to her future success as an independent health services investigator focused on the improvement of patient- centered outcomes in children hospitalized with complex medical and surgical conditions. The K99 research plan outlined in Aim 1 will use quantitative and qualitative methods to explore hospital-specific organizational factors that distinguish high versus low performance in SSI prevention (as determined by adjusted rates of SSI). In addition to providing Dr. McLeod with mentorship and rigorous training in mixed method research, completion of this project will generate hypotheses about organizational barriers and facilitators to the effective implementation of SSI prevention practices. These findings will then serve as the foundation for the R00 proposal (Aim 2) to independently execute a multi-center trial comparing the effectiveness of existing implementation strategies at low performing hospitals to the effectiveness of a tailored (informed by Aim1 barriers/facilitators), multi-disciplinary approach to designing, implementing, and evaluating a patient-focused and patient-informed intervention to reduce SSIs and the preventable harms resulting from them. Applying the skills and training acquired during the K99 phase, this trial will use a novel mixed method approach that addresses limitations in prior research by (1) allowing for the exploration of contextual factors that are not readily measured using quantitative methods alone, and (2) involving at all stages family perspectives on barriers and facilitators to improving quality and outcomes of care for their children. To accomplish her transition, Dr. McLeod has assembled an outstanding team of mentors led by Ron Keren, MD, MPH and renowned orthopedic surgeon, John Dormans, MD, and will continue to benefit from the rich resources offered by the University of Pennsylvania and Children's Hospital of Philadelphia. Importantly, this research will serve as a proof-of-concept for the use of comprehensive patient-focused strategies for improving the implementation effectiveness of interventions to prevent complications following surgical procedures in children, and will inform future multi-center trials to operationalize and test these strategies at other hospitals and for other conditions.